There are a few GPU-related Sites pages that need to be converted to Markdown.

Note that the Markdown syntax supported by Chromium is a little more general and easier to use than traditional Markdown -- it requires less escaping, for example. (I found that true while writing src/testing/buildbot/README.md.) The tool src/tools/md_browser can be used to preview the results:
https://www.chromium.org/developers/markdown-documentation

The pages that need to be converted are:

https://www.chromium.org/developers/testing/gpu-testing
https://www.chromium.org/developers/testing/gpu-testing/gpu-bot-details
https://www.chromium.org/developers/how-tos/gpu-wrangling

I think ideally these would be put into a new src/docs/gpu/ directory.

There are a couple more peripheral pages that should probably also be converted:

https://www.chromium.org/developers/how-tos/debugging-gpu-related-code

This page and the associated script should probably be removed at this point. The JSON endpoints have changed, and Sheriff-o-Matic now supports the GPU bots.
https://www.chromium.org/developers/how-tos/gpu-wrangling/check_gpu_bots-script